Low temperature storage cabinet

ABSTRACT

A low temperature storage cabinet having a freezing cycle system composed of a compressor, a condenser, a throttle and an evaporator, a cabinet temperature sensor for detecting an inside temperature of the cabinet, and an electric fan provided in the cabinet for circulating cooled air in the interior of the cabinet, wherein the compressor in the freezing cycle system is activated in response to rise of the inside temperature of the cabinet and deactivated in response to a fall in the inside temperature of the cabinet, and wherein the rate of operation of the electric fan is decreased in accordance with a decrease of temperature or pressure of refrigerant in the freezing cycle system during deactivation of the compressor to thereby reduce consumption of the electric power.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a low temperature storage cabinet suchas a refrigerator, a freezer or the like in which operation of arefrigerant compressor in a freezing cycle system is controlled tomaintain the interior of the cabinet at a predetermined low temperature,and more particularly to a low temperature storage cabinet in which therate of operation of an electric fan in the cabinet is controlled duringdeactivation of the compressor.

2. Description of the Prior Art

Disclosed in Japanese Utility Model Publication No. 62-29909 is a lowtemperature storage cabinet of this kind in which the electric fan inthe cabinet is operated only for a period of time set by a start switchduring deactivation of the compressor for decreasing a difference intemperature between upper and lower compartments in the cabinet and isstopped only for a period of time set by a stop switch for saving theelectric power.

In the conventional low temperature storage cabinet, a difference intemperature between the upper and lower compartments in the cabinet isestimated by a user for setting each period of time for control of theelectric fan in the cabinet. If there is an error in estimation of thedifference in temperature between the upper and lower compartments orthe period of time is erroneously determined by the user, the differencein temperature between the upper and lower compartments becomes large,and consumption of the electric power may not be properly reduced inaccordance with the inside temperature of the cabinet.

SUMMARY OF THE INVENTION

It is, therefore, a primary object of the present invention to provide alow temperature storage cabinet when operation of electric fan in thecabinet is controlled in accordance with a difference in pressurebetween upper and lower compartments of the cabinet to reduceconsumption of the electric power without causing any problem discussedabove.

According to the present invention, the object is accomplished byproviding a low temperature storage cabinet having a freezing cyclesystem composed of a compressor, a condenser, a throttle and anevaporator, a cabinet temperature sensor for detecting an insidetemperature of the cabinet and for producing an electric signalindicative of the detected inside temperature, compressor control meansresponsive to the electric signal from the temperature sensor foractivating the compressor in the freezing cycle system in response torise of the inside temperature of the cabinet and for deactivating thecompressor in response to a fall in the inside temperature of thecabinet, and an electric fan provided in the cabinet for circulatingcooled air in the interior of the cabinet, wherein the low temperaturestorage cabinet comprises refrigerant temperature detection meansprovided in the freezing cycle system to detect a temperature ofrefrigerant in the freezing cycle system, and fan control means forcontrolling operation of the electric fan in the cabinet in accordancewith a temperature of refrigerant detected by the detection means duringdeactivation of the compressor and for decreasing the rate of operationof the electric fan in accordance with a decrease of the refrigeranttemperature.

According to an aspect of the present invention, there is provided a lowtemperature storage cabinet having a freezing cycle system composed of acompressor, a condenser, a throttle and an evaporator, a cabinettemperature sensor for detecting an inside temperature of the cabinetand for producing an electric signal indicative of the detected insidetemperature, compressor control means responsive to the electric signalfrom the temperature sensor for activating the compressor in thefreezing cycle system in response to rise of the inside temperature ofthe cabinet and for deactivating the compressor in response to a fall inthe inside temperature of the cabinet, and an electric fan provided inthe cabinet for circulating cooled air in the interior of the cabinet,wherein the low temperature storage cabinet comprises refrigerantpressure detection means provided in the freezing cycle system fordetecting pressure of refrigerant in the freezing cycle system, and fancontrol means for controlling operation of the electric fan in thecabinet in accordance with refrigerant pressure detected by the pressuredetection means during deactivation of the compressor and for decreasingthe rate of operation of the electric fan in accordance with a decreaseof the refrigerant pressure.

According to another aspect of the present invention, there is provideda low temperature storage cabinet having a freezing cycle systemcomposed of a compressor, a condenser, a throttle and an evaporator, acabinet temperature sensor for detecting an inside temperature of thecabinet and for producing an electric signal indicative of the detectedinside temperature, compressor control means responsive to the electricsignal from said temperature sensor for activating the compressor in thefreezing cycle system in response to rise of the inside temperature ofthe cabinet and for deactivating the compressor in response to a fall inthe inside temperature of the cabinet, and an electric fan provided inthe cabinet for circulating cooled air in the interior of the cabinet,wherein the low temperature storage cabinet comprises ambienttemperature detection means provided on the cabinet to detect atemperature of outside air, and fan control means for controllingoperation of the electric fan in the cabinet in accordance with atemperature of outside air detected by the ambient temperature detectionmeans during deactivation of the compressor and for decreasing the rateof operation of the electric fan in accordance with a decrease of thetemperature of outside air.

In each practical embodiment of the low temperature storage cabinetsdescribed above, it is preferable that the fan control means comprisesmeans for intermittently operating the electric fan in the cabinetduring deactivation of the compressor and for changing the operationtime and the stopping time of the electric fan to control the rate ofoperation of the electric fan. It is also preferable that the fancontrol means comprises means for selectively effecting continualoperation of the electric fan or intermittent operation of the electricfan during deactivation of the compressor to control the rate ofoperation of the electric fan.

According to a further aspect of the present invention, there isprovided a low temperature storage cabinet having a freezing cyclesystem composed of a compressor, a condenser, a throttle and anevaporator, a cabinet temperature sensor for detecting an insidetemperature of the cabinet and for producing an electric signalindicative of the detected inside temperature, temperature setting meansfor setting an inside temperature of the cabinet, compressor controlmeans responsive to the electric signal from the cabinet temperaturesensor for activating the compressor when the inside temperature of thecabinet rises in a nominal value more than inside temperature set by thetemperature setting means and for deactivating the compressor when theinside temperature of the cabinet falls in the nominal value less thanthe inside temperature set by the temperature setting means, and anelectric fan provided in the cabinet for circulating cooled air in theinterior of the cabinet, wherein the low temperature storage cabinetcomprises refrigerant temperature detection means for detecting atemperature of refrigerant in the freezing cycle system, first fancontrol means for operating the electric fan in the cabinet at apredetermined rate of operation during deactivation of the compressorwhen the inside temperature set by the temperature setting means is lessthan a predetermined temperature, and second fan control means fordecreasing the rate of operation of the electric fan in accordance witha decrease of the refrigerant temperature detected by the refrigeranttemperature detection means during deactivation of the compressor whenthe inside temperature set by the temperature setting means is more thanthe predetermined temperature.

According to an aspect of the present invention, there is provided a lowtemperature storage cabinet having a freezing cycle system composed of acompressor, a condenser, a throttle and an evaporator, a cabinettemperature sensor for detecting an inside temperature of the cabinetand for producing an electric signal indicative of the detected insidetemperature, temperature setting means for setting an inside temperatureof the cabinet, compressor control means responsive to the electricsignal from the cabinet temperature sensor for activating the compressorwhen the inside temperature of the cabinet rises in a nominal value morethan an inside temperature set by the temperature setting means and fordeactivating the compressor when the inside temperature of the cabinetfalls in the nominal value less than the inside temperature set by thetemperature setting means, and an electric fan provided in the cabinetfor circulating cooled air in the interior of the cabinet, wherein thelow temperature storage cabinet comprises refrigerant pressure detectionmeans for detecting pressure of refrigerant in the freezing cyclesystem, first fan control means for operating the electric fan in thecabinet at a predetermined rate of operation during deactivation of thecompressor when the inside temperature set by the temperature settingmeans is less than a predetermined temperature, and second fan controlmeans for decreasing the rate of operation of the electric fan inaccordance with a decrease of the refrigerant pressure detected by therefrigerant pressure detection means during deactivation of thecompressor when the inside temperature set by the temperature settingmeans is more than the predetermined value.

According to another aspect of the present invention, there is provideda low temperature storage cabinet having a freezing cycle systemcomposed of a compressor, a condenser, a throttle and an evaporator,cabinet temperature sensor for detecting an inside temperature of thecabinet and for producing an electric signal indicative of the detectedinside temperature, temperature setting means for setting an insidetemperature of the cabinet, compressor control means responsive to theelectric signal from the cabinet temperature sensor for activating thecompressor when the inside temperature of the cabinet rises in a nominalvalue more than an inside temperature set by the temperature settingmeans and for deactivating said compressor when the inside temperatureof the cabinet falls in the nominal value less than the insidetemperature set by the temperature setting means, and an electric fanprovided in the cabinet for circulating cooled air in the interior ofthe cabinet, wherein the low temperature storage cabinet comprisesambient temperature detection means for detecting a temperature ofoutside air, first fan control means for operating the electric fan inthe cabinet at a predetermined rate of operation during deactivation ofthe compressor when the inside temperature set by the temperaturesetting means is less than a predetermined value, and second fan controlmeans for decreasing the rate of operation of the electric fan inaccordance with a decrease of the temperature of outside air detected bythe ambient temperature detection means during deactivation of thecompressor when the inside temperature set by the temperature settingmeans is more than the predetermined value.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will bemore readily appreciated from the following detailed description ofpreferred embodiments thereof when taken together with the accompanyingdrawings, in which:

FIG. 1 is a vertical sectional view of a refrigerator in accordance withthe present invention;

FIG. 2 is a block diagram of an electric control apparatus for therefrigerator shown in FIG. 1;

FIG. 3 is a time chart showing each operation of a refrigerantcompressor, a condenser fan and an electric fan in the cabinet of therefrigerator;

FIG. 4 is a flow chart of a main program executed by a microcomputer inthe electric control apparatus shown in FIG. 2;

FIG. 5 is a flow chart of a cabinet fan control routine shown in FIG. 4;

FIG. 6 is a flow chart of a modification of the cabinet fan controlroutine shown in FIG. 5;

FIG. 7 is a flow chart of a modification of the main program shown inFIG. 4;

FIG. 8 is a flow chart of another modification of the main program shownin FIG. 4;

FIG. 9 is a block diagram of a modification of the electric controlapparatus shown in FIG. 2;

FIG. 10 is a flow chart of a main program executed by the microcomputershown in FIG. 9;

FIG. 11 is a flow chart of a cabinet fan control routine shown in FIG.10;

FIG. 12 is a flow chart of a timer interruption program executed by themicroprocessor shown in FIG. 9;

FIG. 13 is a flow chart of a modification of the cabinet fan controlroutine shown in FIG. 11;

FIG. 14 is a flow chart of a modification of the main program executedby the microcomputer shown in FIG. 9; and

FIG. 15 is a flow chart of another modification of the main programexecuted by the microcomputer shown in FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 of the drawings, there is schematically illustrated a lowtemperature storage cabinet in the form of a refrigerator which includesa cabinet 10 the interior of which is subdivided by a partition plate 11into a cooling compartment 12a and a storage compartment 12b forpreservation of foodstuffs. Mounted on the partition plate 11 is anevaporator 13 which acts to evaporate compressed refrigerant suppliedthereto from a compressor 14 through a condenser 15, a dryer 16 and athrottle 17 for cooling the interior of cooling compartment 12a and torecirculate the evaporated refrigerant into the compressor 14. In therefrigerator, a freezing cycle system is composed of the evaporator 13,compressor 14, condenser 15, dryer 16 and throttle 17. In the cabinet10, an electric fan 18 is mounted on the partition plate 11 within thecooling compartment 12a to introduce the air from storage compartment12b into the cooling compartment 12a and to circulate the cooled airfrom the cooling compartment 12a into the interior of storagecompartment 12b. The condenser 15 is provided with an electric coolingfan 19.

An electric control apparatus 20A for control of the compressor 14, theelectric fan 18 in cabinet 10 and the cooling fan 19 of condenser 15 iscontained in a control box 20 mounted within the refrigerator. As shownin FIG. 2, the electric control apparatus 20A includes a microcomputer21 provided with a timer 21a and a driving circuit 23. The microcomputer21 is applied with detection signals from a thermo-switch 23, arefrigerant temperature sensor 24 and a saving switch 25 to execute mainprogram shown by a flow chart in FIGS. 4 and 5 for control of eachoperation of the compressor 14, the electric fan 18 in cabinet 10 andthe condenser fan 19.

As shown in FIG. 1, the thermo-switch 23 is arranged within the coolingcompartment 12a to detect an inside temperature of the coolingcompartment 12b and storage compartment 12b for producing an electricsignal indicative of the inside temperature of the cabinet 10. Thethermo-switch 23 is turned on when the inside temperature of the cabinet10 rises more than a predetermined temperature and is turned off whenthe inside temperature of the cabinet 10 drops below the predeterminedtemperature. The refrigerant temperature sensor 24 is mounted on anoutlet conduit of condenser 15 to detect a temperature of therefrigerant for producing an electric signal indicative of therefrigerant temperature. The saving switch 25 is mounted on an operationpanel (not shown) to activate the refrigerator at a saving mode forreducing consumption of the electric power.

Assuming that a power source switch of the refrigerator has been closed,the microcomputer 21 starts to execute the main program at step 100 ofFIG. 4 and repeats execution of processing at step 102 to 112. When thethermo-switch 23 is turned on in response to rise or the insidetemperature of cabinet 10 during execution of the main program, thecomputer 21 determines a “Yes” answer at step 102 and maintains eachoperation of the compressor 14, the condenser fan 19 and the electricfan 18 in cabinet 10 by processing at step 104 and 106. Thus, thefreezing cycle system is maintained in an activated condition to coolthe interior of cooling compartment 12a, and the cooled air from coolingcompartment 12 is circulated by operation of the electric fan 18 intothe storage compartment 12b so that the inside temperature of cabinet 10is uniformly lowered. When the thermo-switch 23 is turned off due todrop of the inside temperature of cabinet 10, the computer 21 determinesa “No” answer at step 102 and stops each operation of the compressor 14and condenser fan 19 at step 108 to deactivate the freezing cycle systemand determines at step 110 whether the saving switch 25 has been turnedon or not. If the answer at step 110 is “No”, the computer 21 returnsthe program to step 102 and maintains the operation of the electric fan18 in cabinet 10 even when the freezing cycle system is deactivated.When the thermo-switch 23 is turned on due to rise of the insidetemperature of cabinet 10 caused by opening and closing of the cabinetdoor, the computer 21 determines a “Yes” answer at step 102 andactivates the freezing cycle system by processing at step 104 and 106.With such control of the freezing cycle system, the inside temperatureof cabinet 10 is maintained approximately at the predeterminedtemperature.

When the saving switch 25 is turned on, the computer 21 determines a“Yes” answer at step 110 and causes the program to proceed to step 112for execution of a cabinet fan control routine shown in FIG. 5. Whenstarted execution of the cabinet fan control routine at step 200, thecomputer 21 is applied with an electric signal indicative of atemperature T of the refrigerant detected by sensor 24 and executesprocessing at step 204 to 212 for setting a measurement time of timer21a in accordance with the refrigerant temperature T. When therefrigerant temperature T is more than a first predetermined value T₁(for instance, 50° C.), the measurement time is defined by a firstpredetermined time TM₁ (for instance, one and half minutes). When therefrigerant temperature T is less than the first predetermined value T₁and more than a second predetermined value T₂ (for instance, 30° C.)less than the first predetermined value T₁, the measurement time isdefined by a second predetermined time TM₂ (for instance, two and halfminutes). When the refrigerant temperature T is less than the secondpredetermined value T₂, the measurement time is defined by a thirdpredetermined time TM₃ (for instance, three minutes). Thus, themeasurement time of timer 21a is successively increased in accordancewith a decrease of the refrigerant temperature T.

After processing at step 204 to 212, the timer 21a starts to count downthe measurement time, while the computer 21 repeats execution ofprocessing at step 214 to 220 unless the saving switch 25 is turned offor the thermo-switch 23 is turned on. Thus, the electric fan 18 incabinet 10 is deactivated by processing at 218 during execution ofprocessing at step 214 to 220. When the timer 21a finishes countdown ofthe measurement time, the computer 21 determines a “Yes” answer at step216 and causes the program to proceed to step 222.

At step 222, the computer 21 defines the measurement time of timer 21aas a fourth predetermined time TM4 (for instance, fifteen seconds)regardless of the refrigerant temperature T. In such an instance, thetimer 21a starts to count down the measurement time TM₄, while thecomputer 21 repeats execution of processing at step 224 to 230 unlessthe saving switch 25 is turned off or the thermo-switch 23 is turned on.Thus, the electric fan 18 in cabinet 10 is operated by processing atstep 228 during execution of processing at step 224 to 230. When thetimer 21a finishes countdown of the measurement time, the computer 21determines a “Yes” answer at step 226 and finishes execution of thecabinet fan control routine at step 234.

When the saving switch 25 is turned on in a condition where thethermo-switch 23 has been turned off to deactivate the freezing cyclesystem, the electric fan 18 in cabinet 10 is operated for the fourthpredetermined time TM₄ and is intermittently stopped for thepredetermined times TM₁, TM₂, TM₃. (see FIG. 3) When the thermo-switch23 is turned on due to rise of the inside temperature of cabinet 10during execution of processing at step 214 to 220 and 224 to 230, thecomputer 21 determines a “Yes” answer respectively at step 220 and 230and finishes execution of the cabinet fan control routine at step 234.In such an instance, the computer 21 determines a “Yes” answer at step102 of FIG. 4 and activates the freezing cycle system. If the savingswitch 25 is turned off during execution of processing at step 214 to220 and 224 to 230, the computer 21 determines a “No” answerrespectively at step 214 and 224 and finishes execution of the cabinetfan control routine at step 234 after operated the electric fan 18 incabinet 10. In this instance, the electric fan 18 in cabinet 10 isoperated even when the freezing cycle system is deactivated.

As is understood from the above description, when the saving switch 25is turned on, the electric fan 18 in cabinet 10 is intermittentlyoperated and stopped in a condition where the freezing cycle system isdeactivated. Although in such an instance, the operation time ofelectric fan 18 is defined by the predetermined time TM₄, the stoppingtime of electric fan 18 is successively increased to the predeterminedtimes TM₁, TM₂ and TM₃ in accordance with a decrease of the refrigeranttemperature T. As a result, the rate of operation of electric fan 18 isdecreased in accordance with a fall in the refrigerant temperature T.

The refrigerant temperature T utilized for control of the rate ofoperation of electric fan 18 in cabinet 10 rises in a condition wherethe difference in temperature between the upper and lower compartmentsof cabinet 10 increases due to rise of the temperature of outside air oropening and closing of the cabinet door. Thus, the rate of operation ofthe compressor 14 in the freezing cycle system is increased inaccordance with the rise of the refrigerant temperature T. Accordingly,even when the rate of operation of electric fan 18 is decreased inaccordance with a fall in the refrigerant temperature, the insidetemperature of cabinet 10 is uniformly maintained at the predeterminedvalue without increasing the difference in temperature between the upperand lower compartments of cabinet 10. This is useful to automaticallyreduce consumption of the electric power in a reliable manner.

Although in the foregoing embodiment, the stopping time of electric fan18 is changed at three steps in accordance with the refrigeranttemperature T in a condition where the saving switch 25 has been turnedon, the stopping time of electric fan 18 may be changed at two steps ormore than four steps.

Illustrated in FIG. 6 is a modification of the cabinet fan controlroutine shown in FIG. 5, wherein the computer 21 is programmed tocontinuously operate the electric fan 18 in cabinet 10 by processing atstep 232 when the refrigerant temperature T is more than thepredetermined value T₁ (for instance, 50° C.). During execution of thecabinet fan control routine shown in FIG. 5, the computer 21 determinesat step 204 whether the refrigerant temperature T is more than thepredetermined value T₁ or not. If the answer at step 204 is “Yes”, thecomputer 21 operates the electric fan 18 in cabinet 10 at step 232 inthe same manner as in the foregoing embodiment and finishes execution ofthe cabinet fan control routine at step 234. If the refrigeranttemperature is less than the predetermined value T₁, the computer 21determines a “No” answer at step 204 and executes processing at step206, 210a, 212a, 214 to 220 and processing at step 222a, 222b, 222c, 224to 230 to intermittently operate the electric fan 18 in cabinet 10. As aresult, during deactivation of the freezing cycle system, the rate ofoperation of electric fan 18 in cabinet 10 is decreased in accordancewith a fall in the refrigerant temperature T.

In addition, the cabinet fan control routine shown in FIG. 6 ischaracterized in that both the stopping time and the operation time ofelectric fan 18 are changed in accordance with the refrigeranttemperature T during deactivation of the freezing cycle system. When therefrigerant temperature T is less than the predetermined value T₁ andmore than the predetermined value T₂ (for instance, 30° C.), thepredetermined value TM₁ (for instance, two and half minutes) is set asthe measurement time of timer 21a by processing at step 204, 206 and210a. When the refrigerant temperature T is less than the predeterminedvalue T₂, the predetermined value TM₂ (for instance, three minutes) isset as the measurement time of timer 21a by processing at step 204, 206and 212a. Subsequently, the stopping time of electric fan 18 is set inaccordance with the refrigerant temperature T by processing at step 216and 218.

After processing at step 216, the computer 21 determines at step 222awhether the refrigerant temperature T is more than the predeterminedvalue T₂ or not. If the answer at step 222a is “Yes”, the predeterminedvalue TM₂ (for instance, twenty minutes) is set as the measurement timeof timer 21a by processing at step 222b. If the answer at step 222a is“No”, the predetermined value TM₄ (for instance, fifteen minutes) is setas the measurement time of timer 21a by processing at step 222c.Subsequently, the operation time of electric fan 18 is set in accordancewith the refrigerant temperature T by processing at step 226 and 228.

With such execution of the cabinet fan control routine shown in FIG. 6,the rate of operation of electric fan 18 in cabinet 10 is determined byboth the stopping time and the operation time described above duringdeactivation of the freezing cycle system. That is to say, when therefrigerant temperature T is less than the predetermined value T₁ andmore than the predetermined value T₂, the rate of operation of electricfan 18 is defined by TM₃/(TM₁+TM₃). When the refrigerant temperature Tis less than the predetermined value T₂, the rate of operation ofelectric fan 18 is defined by TM₄/(TM₂+TM₄). As the values TM₁-TM₄ aredetermined in such a manner that the rate of operation TM₃/(TM₁+TM₃)becomes larger than the rate of operation TM₄/(TM₂+TM₄), the rate ofoperation of the electric fan 18 during deactivation of the freezingcycle system is decreased in accordance with a fall in the refrigeranttemperature in the same manner as in the foregoing embodiment.Accordingly, consumption of the electric power can be automaticallyreduced without increasing the difference in temperature between theupper and lower compartments of cabinet 10.

In a practical embodiment of the present invention, an additionalelectric fan 31 may be further provided within the cabinet 10 as shownby broken lines in FIG. 1, and the main program shown in FIG. 4 may bemodified as shown in FIG. 7 to selectively operate the electric fans 18and 31 in cabinet 10 in accordance with the refrigerant temperature T ina condition where the saving switch 25 is turned on during deactivationof the freezing cycle system. During execution of the modified mainprogram, the computer 21 activates and deactivates the freezing cyclesystem in response to the detection signal applied from thethermo-switch 23 by processing at step 102, 104 and 108. In a conditionwhere the freezing cycle system is being activated or the saving switch23 is turned off during deactivation of the freezing cycle system, thecomputer 21 operates both the electric fans 18 and 31 in cabinet 10 byprocessing at step 106a. When the saving switch 25 is turned on duringdeactivation of the freezing cycle system, the computer 21 determines a“Yes” answer at step 110, reads out the refrigerant temperature T fromsensor 24 and determines at step 122 whether the refrigerant temperatureT is more than the first predetermined value T₁ or not. When the answerat step 122 is “Yes”, the computer 21 operates both the electric fans 18and 31 in cabinet 10 by processing at step 106a. When the answer at step122 is “No”, the computer 21 operates only one of the electric fans 18and 31 by processing at step 124. Thus, the rate of operation ofelectric fans 18 and 31 in cabinet 10 is decreased in accordance with adecrease of the refrigerant temperature T during deactivation of thefreezing cycle system to reduce consumption of the electric power.

In the practical embodiment described above, a speed control circuit 41may be disposed between the driving circuit 22 and the electric fan 18in cabinet 10, as shown by broken lines in FIG. 2. In this embodiment,the speed control circuit 41 is provided in the form of an inverter orphase control circuit for controlling the rotation speed of electric fan18, and the main program of FIG. 4 is modified as shown in FIG. 8 tocontrol the rotation speed of electric fan 18 in accordance with therefrigerant temperature T in a condition where the saving switch 25 isturned on during deactivation of the freezing cycle system. Duringexecution of the modified main program, the computer 21 activates anddeactivates the freezing cycle system in response to the detectionsignal applied from the thermo-switch 23 by processing at step 102, 104and 108. In a condition where the freezing cycle system is beingactivated or the saving switch 25 is maintained in its off-positionduring deactivation of the freezing cycle system, the computer 21 causesthe speed control circuit 41 at step 106b to operate the electric fan 18in cabinet 10 at a maximum speed. When the saving switch 25 is turned onduring deactivation of the freezing cycle system, the computer 21determines a “Yes” answer at step 110, reads out the refrigeranttemperature T from sensor 24 at step 120 and determines at step 122whether the refrigerant temperature T is more than the firstpredetermined value T₁ (for instance, 40° C.) or not. When the answer atstep 122 is “Yes”, the computer 21 causes the speed control circuit 41at step 106b to rotate the electric fan 18 at the maximum speed. Whenthe answer at step 122 is “No”, the computer 21 causes the speed controlcircuit 41 at step 124a to decrease the rotation speed of the electricfan 18 in cabinet 10. Thus, the rate of operation of electric fan 18 incabinet 10 is decreased in accordance with a decrease of the refrigeranttemperature T during deactivation of the freezing cycle system to reduceconsumption of the electric power.

In a modification of the foregoing embodiment, the refrigeranttemperature sensor 24 may be replaced with a refrigerant pressure sensor42 disposed between the condenser 15 and dryer 16 for detectingrefrigerant pressure in the freezing cycle system, as shown by brokenlines in FIGS. 1 and 2. In this modification, the computer 21 isprogrammed to decrease the rate of operation of electric fan 18 incabinet 10 in accordance with a decrease of refrigerant pressure Pdetected by sensor 42.

In another modification of the foregoing embodiment, an outside airtemperature sensor 43 may be provided on the cabinet 10 for detectingthe temperature of outside air as shown by broken lines in FIGS. 1 and2. In this modification, the computer 21 is programmed to decrease therate of operation of electric fan 18 in cabinet 10 in accordance with adecrease of the outside air temperature detected by sensor 43.

Illustrated in FIG. 9 is a modification of the electric controlapparatus shown in FIG. 2, wherein the computer 21 is connected to atemperature setting switch 26, a temperature rising switch 27a and atemperature drop switch 27b for setting an inside temperature of thecabinet 10 in a desired value and a display 28 for indicating thereonthe inside temperature of the cabinet 10 and a temperature setting mode,and wherein the thermo-switch 23 is replaced with an cabinet temperaturesensor 23a mounted within the cooling compartment 12a to detect aninside temperature C of the cabinet 10. In this modification, thecomputer 21 is provided with an additional timer 21b for execution of atimer interruption program shown in FIG. 12 and is programmed to executea main program and a cabinet fan control routine respectively shown inFIGS. 10 and 11 and to execute the timer interruption program undercontrol of the timer 21b.

Assuming that the power source switch of the refrigerator has beenclosed, the computer 21 starts to execute the main program shown in FIG.10 at step 150 and sets an initial value Co indicative of a standardinside temperature of the cabinet 10 as a set temperature Cs at step152. At step 152, the computer 21 further sets a first flag FLG1 to “1”and a second flag FLG2 to “0”. The first flag FLG1 represents activationof the compressor 14 when it is set to “1” and represents deactivationof the compressor 14 when it is set to “0”. The second flag FLG2represents a non-saving mode of the electric power when it is set to “0”and represents a saving mode of the electric power when it is set to“1”. Thus, the computer 21 activates the compressor 14, condenser fan 19and cabinet fan 18 at step 154 to cool the interior of coolingcompartment 12a and to circulate the cooled air into the storagecompartment 12b from the cooling compartment 21a.

After processing at step 152 and 154, the computer 21 repeats executionof processing at step 156 to 174. If the first flag FLG1 is “1”, thecomputer 21 determines a “Yes” answer at step 156 and determines at step158 whether or not an inside temperature C of the cabinet 10 detected bysensor 23a is less than a lower limit temperature Cs−ΔC1 defined by adifference between the set temperature Cs and a nominal temperature ΔC1(for instance, 2° C.). If the answer at step 158 is “No”, the computer21 repeats processing at step 156 and 158. If the answer at step 158 is“Yes”, the computer 21 deactivates the compressor 14 and condenser fan19 at step 160 and sets the first flag FLG1 to “0” indicative ofdeactivation of the compressor 14 at step 162. Subsequently, thecomputer 21 determines at step 164 whether the second flag FLG2 is “1”or not. If the second flag FLG2 is set as “0” at the initial setting,the computer 21 determines “No” answer at step 164 and maintains theoperation of cabinet fan 18 at step 174.

When the program is returned to step 156 after processing at step 174,the computer 21 determines a “No” answer at step 156 and causes theprogram to proceed to step 168. At step 168, the computer 21 determineswhether or not the inside temperature of the cabinet 10 detected bysensor 23a is more than an upper limit temperature Cs+ΔC2 defined by thesum of the set temperature Cs and a nominal temperature ΔC2 (forinstance, 1.5° C.). If the answer at step 168 is “No”, the computer 21repeats processing at step 164, 174, 156 and 168 during which thefreezing cycle system is deactivated.

When the inside temperature C of the cabinet 10 becomes more than theupper limit temperature Cs+ΔC2, the computer 21 determines a “Yes”answer at step 168 and activates the compressor 14 and condenser fan 19at step 170 to cool the interior of cooling compartment 12a and storagecompartment 12b. After processing at step 170, the computer 21 sets thefirst flag FLG1 to “1” at step 172 and maintains the operation ofcabinet fan 18 by processing at step 174. With such processing at step156 to 164 and 168 to 174, the freezing cycle system is repeatedlyactivated and deactivated to maintain the inside temperature C ofcooling compartment 12a and storage compartment 12b approximately at theset temperature Cs between the lower limit temperature Cs−ΔC1 and theupper limit temperature Cs+ΔC2.

During execution of the main program described above, the computer 21executes the timer interruption program of FIG. 12 under control of thetimer 21b at a predetermined time interval. When started to execute thetimer interruption program at step 300, the computer 21 determines atstep 302 whether the temperature setting switch 26 has been turned on ornot. If the answer at step 302 is “No”, the computer 21 determines atstep 312 whether the drop switch 27b is maintained in its on-positionfor a predetermined time (for instance, five minutes) or not. If theanswer at step 312 is “No”, the computer 21 finishes execution of thetimer interruption program at step 320. If the answer at step 302 is“Yes”, the computer 21 rises the set temperature Cs by processing atstep 304 and 306. When the rising switch 27a is turned on in a conditionwhere the temperature setting switch 26 is being turned on, the computer21 determines a “Yes” answer at step 304 and rises the set temperatureCs with “1” at each lapse of a predetermined time. If the rising switch27a is not turned on, the computer 21 determines a “No” answer at step304 and lowers the set temperature Cs by processing at step 308 and 310.When the drop switch 27b is turned on in a condition where thetemperature setting switch 26 is being turned on, the computer 21determines a “Yes” answer at step 308 and lowers the set temperature Cswith “1” at each lapse of the predetermined time by processing at step310. If the drop switch 27b is not turned on, the computer 21 determinesa “No” answer at step 310 and causes the program to proceed to step 316.

At step 316, the computer 21 causes the display 28 to indicate the settemperature Cs on the display panel. After processing at step 316, thecomputer 21 causes the display 28 at step 318 to indicate whether thepower saving mode is selected or not. When the power saving mode is notselected, the computer 21 causes the display to put out a decimal pointin a lower order of the set temperature Cs. When the power saving modeis selected, the computer 21 causes the display to put on the decimalpoint.

When the set temperature Cs is changed by processing at step 302 to 310,the computer 21 executes processing at step 156 to 164 and 168 to 174 ofFIG. 10 to maintain the inside temperature C of cooling compartment 12aand storage compartment 12b approximately at the set temperature Cs.When the drop switch 27b is maintained in its on-position for apredetermined time in a condition where the temperature setting switch27 is maintained in its off-position, the computer 21 determines a “Yes”answer at step 312 and inverts the second flag FLG2 from “0” to “1” orvice versa at step 314. When the second flag FLG2 is set to “1”, thecomputer 21 determines a “Yes” answer at step 164 of FIG. 10 andexecutes at step 166 a cabinet fan control routine shown in FIG. 11. Thecabinet fan control routine of FIG. 11 is substantially the same as thatof FIG. 5, expect for processing at step 242 to 248.

When started to execute the cabinet fan control routine of FIG. 11 atstep 200, the computer 21 determines at step 242 whether the settemperature Cs is less than a predetermined value Cso (for instance, 0°C.) or not. If the answer at step 242 is “Yes”, the computer 21 sets apredetermined time TM₅ as the measurement time of timer 21a at step 244and causes the program to proceed to step 214. If the answer at step 242is “No”, the computer 21 executes processing at step 202 to 212 in thesame manner as in the foregoing embodiment for setting the predeterminedtime TM₁, TM₂ or TM₃. In this instance, the predetermined time TM₅ isset as a smaller value (for instance, one and half minutes) than thefirst predetermined time TM₁. Accordingly, if the set temperature Cs isless than the predetermined value Cso, the stopping time of electric fan18 defined by processing at step 216 and 218 becomes less than a minimumstopping time defined in a condition where the set temperature Cs ishigher than the predetermined time Cso.

When the program proceeds to step 246 after processing at step 216, thecomputer 21 determines whether the set temperature Cs is less than thepredetermined value Cso (for instance, 0° C.) or not. If the answer atstep 246 is “Yes”, the computer 21 sets a predetermined time TM₆ as themeasurement time of timer 21a at step 248 and causes the program toproceed to step 224. If the answer at step 246 is “No”, the computer 21executes processing at step 222 in the same manner as in the foregoingembodiment for setting the fourth predetermined time TM₄ as themeasurement time of timer 21a. In this instance, the predetermined timeTM₆ is set as a larger value (for instance, fifteen seconds) than thefourth predetermined time TM₄. Accordingly, if the set temperature Cs isless than the predetermined value Cso, the operation time of electricfan 18 defined by processing at step 226 and 228 becomes more than thatin a condition where the set temperature Cs is higher than thepredetermined value Cso.

As a result, when the set temperature Cs is less than the predeterminedvalue Cso at the power saving mode, the rate of operation of electricfan 18 during deactivation of the compressor 14 is fixed to a relativelyhigh value regardlessly of the refrigerant temperature T. Thus, evenwhen the inside temperature of cabinet 10 is set at a lower value than0° C. for preserving fresh foods such as fish, meat and the like in aslightly frozen condition, fluctuation of the inside temperature ofstorage compartment 12b caused by intermittent operation of the electricfan 18 is restrained to prevent the preserved fresh foods from meltingor freezing. In addition, when the set temperature Cs is higher than thepredetermined value Cso, the rate of operation of electric fan 18 incabinet 10 is decreased in accordance with a decrease of the refrigeranttemperature T in the same manner as in the foregoing embodiment toautomatically reduce consumption of the electric power.

Illustrated in FIG. 13 is a modification of the cabinet fan controlroutine of FIG. 6, wherein processing at step 252 is added beforeprocessing at step 202. At step 252, the computer 21 determines whetherthe set temperature Cs is less than the predetermined value Cso (forinstance, 0° C.) or not. If the answer at step 252 is “Yes”, thecomputer 21 causes the program to proceed to step 232 for maintainingthe operation of electric fan 18 in cabinet 10. If the answer at step252 is “No”, the computer 21 executes processing at step 202 to 230 inthe same manner as described above for intermittently operating theelectric fan 18 in cabinet in accordance with the refrigeranttemperature T. Thus, even when the inside temperature of cabinet 10 isset at a lower temperature than 0° C. for preserving fresh foods such asfish, meat and the like in a slightly frozen condition, fluctuation ofthe inside temperature of cabinet 10 is restrained to prevent thepreserved foods from melting or freezing. In addition, when the settemperature Cs is higher than the predetermined value Cso, the rate ofoperation of electric fan 18 in cabinet 10 is decreased in accordancewith a decrease of the refrigerant temperature T to automatically reduceconsumption of the electric power.

Illustrated in FIG. 14 is a modification of the main program shown inFIG. 10 for control of the electric fans 18 and 19 provided in thecabinet 10 as shown in FIGS. 1 and 9. During execution of the mainprogram of FIG. 14, the computer 21 executes the timer interruptionprogram of FIG. 12. In this modification, the main program is programmedto selectively operate the electric fans 18 and 19 in accordance withthe set temperature Cs and refrigerant temperature T at the power savingmode during deactivation of the freezing cycle system.

During execution of the main program of FIG. 14, the computer 21intermittently activates and deactivates the freezing cycle system inaccordance with the inside temperature of cabinet 10 by processing atstep 152 to 162 and 168 to 172. When the freezing cycle system isactivated or the second flag FLG2 is set as “0” during deactivation ofthe freezing cycle system, the computer 21 operates both the electricfans 18 and 19 in cabinet 10 by processing at step 174a. When the secondflag FLG2 is set as “1” during deactivation of the freezing cyclesystem, the computer 21 determines a “Yes” answer at step 180 anddetermines at step 182 whether the set temperature Cs is less than thepredetermined value Cso as in the foregoing modification. If the answerat step 182 is “Yes”, the computer 21 operates both the electric fans 18and 19 in cabinet 10 by processing at step 174a. If the answer at step182 is “No”, the computer 21 reads out the refrigerant temperature Tdetected by sensor 24 at step 184 and selectively operates the electricfans 18 and 19 in accordance with the refrigerant temperature T byprocessing at step 186, 174 and 188.

With such control of the electric fans 18 and 19 as described above,even when the inside temperature of cabinet 10 is set at a lowertemperature than 0° C. for preserving fresh foods such as fish, meat andthe like in a lightly frozen condition, fluctuation of the insidetemperature of storage compartment 12b is retrained to prevent thepreserved foods from melting or freezing.

Illustrated in FIG. 15 is another modification of the main program shownin FIG. 10 for control of the electric fan 18 in the electric controlapparatus shown in FIG. 9. During execution of the main program of FIG.15, the computer 21 executes the timer interruption program of FIG. 2.In this modification, the main program is programmed to control therotation speed of electric fan 18 in accordance with the set temperatureCs and refrigerant temperature T when the freezing cycle system isdeactivated at the power saving mode.

During execution of the main program of FIG. 15, the computer 21intermittently activates and deactivates the freezing cycle system inaccordance with the inside temperature C of cabinet 10 by processing atstep 152 to 162 and 168 to 172. When the freezing cycle system isactivated or the second flag FLG 2 is set as “0” during deactivation ofthe freezing cycle system, the computer 21 operates the electric fan 18in cabinet 10 at a maximum rotation speed by processing at step 174b.When the second flag FLG2 is set as “1” during deactivation of thefreezing cycle system, the computer 21 executes processing at step 182to 186 to decrease the rotation speed of electric fan 18 under controlof the speed control circuit 41 when the refrigerant temperature T isless than the predetermined value T₁ in a condition where the settemperature Cs is higher than the predetermined value Cso. When therefrigerant temperature T is more than the predetermined value T₁ or theset temperature Cs is lower than the predetermined value Cso, thecomputer 21 operates the electric fan 18 at the maximum rotation speedby processing at step 174b.

With such control of the electric fan 18 as described above, even whenthe inside temperature of cabinet 10 is set at a lower temperature than0° C. for preserving fresh foods such fish, meat and the like in aslightly frozen condition, fluctuation of the inside temperature ofcabinet 10 is restrained to prevent the preserved foods from melting orfreezing. In addition, when the set temperature Cs is higher than thepredetermined value Cso to preserve fresh foods without causing anyspoil thereof, the rate of operation of the electric fan 18 is decreasedin accordance with a decrease of the refrigerant temperature T toautomatically reduce consumption of the electric power.

1. A low temperature storage cabinet having a freezing cycle system composed of a compressor, a condenser, a throttle and an evaporator, a cabinet temperature sensor for detecting an inside temperature of the cabinet and for producing an electric signal indicative of the detected inside temperature, compressor control means responsive to the electric signal from said temperature sensor for activating the compressor in the freezing cycle system in response to rise of the inside temperature of the cabinet and for deactivating the compressor in response to a fall in the inside temperature of the cabinet, and an electric fan provided in the cabinet for circulating cooled air in the interior of the cabinet, wherein the low temperature storage cabinet comprises: refrigerant temperature detection means provided in the freezing cycle system to detect a temperature of refrigerant in the freezing cycle system; and fan control means for controlling operation of said electric fan in the cabinet in accordance with a temperature of refrigerant detected by said detection means during deactivation of said compressor and for decreasing the rate of operation of said electric fan in accordance with a decrease of the refrigerant temperature.
 2. A low temperature storage cabinet as claimed in claim 1, wherein said fan control means comprises means for intermittently operating said electric fan in the cabinet during deactivation of said compressor and for changing the operation time and the stopping time of said electric fan to control the rate of operation of said electric fan in accordance with the refrigerant temperature.
 3. A low temperature storage cabinet as claimed in claim 1, wherein said fan control means comprises means for selectively effecting continual operation of said electric fan or intermittent operation of said electric fan during deactivation of said compressor to control the rate of operation of said electric fan in accordance with the refrigerant temperature.
 4. A low temperature storage cabinet as claimed in claim 1, wherein a plurality of electric fans are provided in the cabinet for circulating cooled air in the interior of the cabinet, and wherein said fan control means comprises means for selectively operating said electric fans during deactivation of said compressor to control the rate of operation of said electric fans in accordance with the refrigerant temperature.
 5. A low temperature storage cabinet as claimed in claim 1, wherein said fan control means comprises means for controlling the rotation speed of said electric fan during deactivation of said compressor to control the rate of operation of said electric fan in accordance with the refrigerant temperature.
 6. A low temperature storage cabinet having a freezing cycle system composed of a compressor, a condenser, a throttle and an evaporator, a cabinet temperature sensor for detecting an inside temperature of the cabinet and for producing an electric signal indicative of the detected inside temperature, compressor control means responsive to the electric signal from said temperature sensor for activating the compressor in the freezing cycle system in response to rise of the inside temperature of the cabinet and for deactivating the compressor in response to a fall in the inside temperature of the cabinet, and an electric fan provided in the cabinet for circulating cooled air in the interior of the cabinet, wherein the low temperature storage cabinet comprises: refrigerant pressure detection means provided in the freezing cycle system to detect pressure of refrigerant in the freezing cycle system; and fan control means for controlling operation of said electric fan in the cabinet in accordance with refrigerant pressure detected by said pressure detection means during deactivation of said compressor and for decreasing the rate of operation of said electric fan in accordance with a decrease of the refrigerant pressure.
 7. A low temperature storage cabinet having a freezing cycle system composed of a compressor, a condenser, a throttle and an evaporator, a cabinet temperature sensor for detecting an inside temperature of the cabinet and for producing an electric signal indicative of the detected inside temperature, compressor control means responsive to the electric signal from said temperature sensor for activating the compressor in the freezing cycle system in response to rise of the inside temperature of the cabinet and for deactivating the compressor in response to a fall in the inside temperature of the cabinet, and an electric fan provided in the cabinet for circulating cooled air in the interior of the cabinet, wherein the low temperature storage cabinet comprises: ambient temperature detection means provided on the cabinet to detect a temperature of outside air; and fan control means for controlling operation of said electric fan in the cabinet in accordance with a temperature of outside air detected by said ambient temperature detection means during deactivation of said compressor and for decreasing the rate of operation of said electric fan in accordance with a decrease of the temperature of outside air.
 8. A low temperature storage cabinet having a freezing cycle system composed of a compressor, a condenser, a throttle and an evaporator, a cabinet temperature sensor for detecting an inside temperature of the cabinet and for producing an electric signal indicative of the detected inside temperature, temperature setting means for setting an inside temperature of the cabinet, compressor control means responsive to the electric signal from said cabinet temperature sensor for activating said compressor when the inside temperature of the cabinet rises in a nominal value more than an inside temperature set by said temperature setting means and for deactivating said compressor when the inside temperature of the cabinet falls in the nominal value less than the inside temperature set by said temperature setting means, and an electric fan provided in the cabinet for circulating cooled air in the interior of the cabinet, wherein the low temperature storage cabinet comprises: refrigerant temperature detection means provided in the freezing cycle system for detecting a temperature of refrigerant in the freezing cycle system; first fan control means for operating said electric fan in the cabinet at a predetermined rate of operation during deactivation of said compressor when the inside temperature set by said temperature setting means is less than a predetermined temperature; and second fan control means for decrease the rate of operation of said electric fan in accordance with a decrease of the refrigerant temperature detected by said refrigerant temperature detection means during deactivation of said compressor when the inside temperature set by said temperature setting means is more than the predetermined temperature.
 9. A low temperature storage cabinet having a freezing cycle system composed of a compressor, a condenser, a throttle and an evaporator, cabinet temperature sensor for detecting an inside temperature of the cabinet and for producing an electric signal indicative of the detected inside temperature, temperature setting means for setting an inside temperature of the cabinet, compressor control means responsive to the electric signal from said cabinet temperature sensor for activating said compressor when the inside temperature of the cabinet rises in a nominal value more than an inside temperature set by said temperature setting means and for deactivating said compressor when the inside temperature of the cabinet falls in the nominal value less than the inside temperature set by said temperature setting means, and an electric fan provided in the cabinet for circulating cooled air in the interior of the cabinet, wherein the low temperature storage cabinet comprises: refrigerant pressure detection means provided in the freezing cycle system for detecting pressure of refrigerant in the freezing cycle system; first fan control means for operating said electric fan in the cabinet at a predetermined rate of operation during deactivation when the inside temperature set by said temperature setting means is less than a predetermined temperature; and second fan control means for decreasing the rate of operation of said electric fan in accordance with a decrease of the refrigerant pressure detected by said refrigerant pressure detection means during deactivation of said compressor when the inside temperature set by said temperature setting means is more than the predetermined temperature.
 10. A low temperature storage cabinet having a freezing cycle system composed of a compressor, a condenser, a throttle and an evaporator, cabinet temperature sensor for detecting an inside temperature of the cabinet and for producing an electric signal indicative of the detected inside temperature, temperature setting means for setting an inside temperature of the cabinet, compressor control means responsive to the electric signal from said cabinet temperature sensor for activating said compressor when the inside temperature of the cabinet rises in a nominal value more than an inside temperature set by said temperature setting means and for deactivating said compressor when the inside temperature of the cabinet falls in the nominal value less than the inside temperature set by said temperature setting means, and an electric fan provided in the cabinet for circulating cooled air in the interior of the cabinet, wherein the low temperature storage cabinet comprises: ambient temperature detection means for detecting a temperature of outside air; first fan control means for operating said electric fan in the cabinet at a predetermined rate of operation during deactivation of said compressor when the inside temperature set by said temperature setting means is less than a predetermined temperature; and second fan control means for decreasing the rate of operation of said electric fan in accordance with a decrease of the temperature of outside air detected by said ambient temperature detection means during deactivation of said compressor when the inside temperature set by said temperature setting means is more than the predetermined temperature.
 11. A low temperature storage cabinet having a freezing cycle system comprising: a compressor, a condenser, a throttle and an evaporator, a cabinet temperature sensor for detecting an inside temperature of the cabinet and for producing an electric signal indicative of the detected inside temperature, temperature setting means for setting an inside temperature of the cabinet to a predetermined temperature, compressor control means responsive to the electric signal from said cabinet temperature sensor for activating said compressor in the freezing cycle system when the inside temperature of the cabinet rises more than the predetermined temperature and for deactivating said compressor when the inside temperature of the cabinet falls to less than the predetermined temperature, and an electric fan provided in the cabinet for circulating cooled air in the interior of the cabinet, wherein the low temperature storage cabinet comprises: fan control means for operating said electric fan in the cabinet at a predetermined rate of operation during deactivation of said compressor in a condition where the inside temperature of the cabinet is set less than the predetermined temperature by adjustment of said temperature setting means and for operating said electric fan at a rate of operation less than the predetermined rate of operation during deactivation of said compressor in a condition where the inside temperature of the cabinet is set more than or equal to the predetermined temperature value by adjustment of said temperature setting means. 